Microwave Medical Imaging

Early time prevention is a key factor in delivering long term survival to breast cancer patients; 95% cure rates are possible if its detected in its early stages. X-ray mammography remains the most effective technique to detect non palpable breast tumors. However, ionizing radiations together with breast compression do not lead to comfort in patient treatment. Moreover, 10-30% of tumors are missed by mammography. The significant number of false negatives can be attributed to the presence of a dense glandular tissue around the tumor, absence of microcalcifications in the early stages and tumors located close to the chest wall or underarm. 

In this context, ultrawideband microwave radar technology is an attractive alternative. The general approach is to illuminate the breast with a UWB pulse from a number of antenna locations. The backscattered waves are collected and post-processed to obtain a high resolution dielectric map of the breast. This approach relies on the contrast between the dielectric properties of normal and malignant tissues at microwave frequencies. The intrinsic contrast is estimated to vary from a minimum of 2:1 to a maximum of 10:1, whereas for X-ray is only a few percent.

Based on these considerations, we investigate the design of a low cost CMOS integrated circuit that can be connected to an array of antennas to perform monostatic or bistatic measurements. Each IC acts as a transceiver, generating stepped frequency waveforms and collecting back the scattered signals from the breast. By means of inverse Fourier transform time-domain waveforms are obtained. From the waveform and the time of flight of the back scattered pulses it is possible to derive information on the reflecting objects, such that their distance and size.